Inside the church, Rick – who plays Louis Litt in the US legal drama – was seen pulling a bizarre facial expression, which quickly went viral on Twitter.

The actor was seen pulling a weird facial expression inside the chapel[BBC]

And after the ceremony, the 47-year-old actor took to Instagram to explain the shocking reason behind his uncomfortable look.

Captioning his video: "Royal Wedding Face.... #brushyourteeth", Rick explained that he looked disgusted in the chapel because he could smell someone's bad breath.

In an video speaking to the camera while chewing gum, Rick said: “Hi. So to answer any questions about the weird face that was made at the wedding, imagine sitting next to people to your right – not knowing which person it was – that has halitosis.

Rick Hoffman was all smiles as he arrives at St George's Chapel at Windsor Castle before the royal wedding [Getty]

"Um. Hence the face. That is apparently all over the place. So it's as simple as that, Charlie. Love you guys. Yah. Halitosis. Disgusting."

His co-star Gabriel Macht's wife Jacinda Barrett, who was still dressed in her wedding outfit, then spoke to the camera as she held up a screenshot of Rick’s viral facial expression.

"I just want to say, that's not the Rick I know," she told the camera.